Geared motor and manufacturing method therefor

ABSTRACT

A geared motor may include a motor and a gear mechanism for transmitting rotation of the motor. The gear mechanism includes an output gear which outputs rotation of the motor and a gear in a preceding stage which is connected with the output gear through another gear and the output gear is formed with a first positioning part showing an angular position of the output gear and the gear in the preceding stage is formed with a second positioning part showing an angular position of the gear in the preceding stage. After an assembling angular position of the output gear and an assembling angular position of the gear in the preceding stage have been determined, another gear is assembled.

CROSS REFERENCE TO RELATED APPLICATION

The present invention claims priority under 35 U.S.C. §119 to JapaneseApplication No. 2011-180858 filed Aug. 22, 2011 and Japanese ApplicationNo. 2011-180859 filed Aug. 22, 2011, the entire contents of which areincorporated herein by reference.

FIELD OF THE INVENTION

At least an embodiment of the present invention may relate to a gearedmotor including a motor and a gear mechanism and to a manufacturingmethod for the geared motor.

BACKGROUND

A geared motor includes a motor and a gear mechanism for transmittingrotation of the motor. In the gear mechanism, a structure in which aprotruded part comprised of a teeth non-formation part is provided inone of the gears and a recessed part comprised of a tooth-missing partis provided in the other of the gears has been proposed as a structurefor matching the phase of the gears with each other (see, JapanesePatent Laid-Open No. 2009-2422).

According to this structure, the phase of the gears can be matched witheach other with the protruded part provided in one of the gears and therecessed part provided in the other of the gears as a reference.

However, in the structure described in Patent Literature 1, the phase ofthe gears directly engaged with each other can be matched but it isdifficult that the phase between gears which are connected with eachother through other gears is matched. Further, when a protruded part anda recessed part formed of a teeth non-formation part are utilized, in agear whose teeth number is small, the meshing ratio is lowered and thusturning of the gear may be performed unsatisfactory.

SUMMARY

In view of the problem described above, at least an embodiment of thepresent invention may advantageously provide a geared motor and amanufacturing method for the geared motor in which the phase between thegears which are not engaged with each other directly is capable of beingmatched.

According to at least an embodiment of the present invention, there maybe provided a geared motor including a motor and a gear mechanism whichtransmits rotation of the motor. The gear mechanism includes an outputgear which outputs rotation of the motor and a gear in a preceding stagewhich is connected with the output gear through another gear, and theoutput gear is formed with a first positioning part showing an angularposition of the output gear and the gear in the preceding stage isformed with a second positioning part showing an angular position of thegear in the preceding stage.

Further, according to at least an embodiment of the present invention,there may be provided a manufacturing method for a geared motorincluding a motor and a gear mechanism for transmitting rotation of themotor. The manufacturing method includes previously providing an outputgear of the gear mechanism for outputting rotation of the motor with afirst positioning part showing an angular position of the output gearand previously providing a gear in a preceding stage of the gearmechanism which is connected with the output gear through another gearwith a second positioning part showing an angular position of the gearin the preceding stage. When the gear mechanism is to be assembled, thefirst positioning part is fitted to a first pin which is stood up at apredetermined angular position with respect to a rotation center of theoutput gear to determine an assembling angular position of the outputgear, and the second positioning part is fitted to a second pin which isstood up at a predetermined angular position with respect to a rotationcenter of the gear in the preceding stage to determine an assemblingangular position of the gear in the preceding stage and, after anassembling angular position of the output gear and an assembling angularposition of the gear in the preceding stage have been determined,another gear is assembled.

In accordance with at least an embodiment of the present invention, theoutput gear is formed with a first positioning part showing an angularposition of the output gear and the gear in the preceding stage which isconnected with the output gear through another gear is formed with asecond positioning part showing an angular position of the gear in thepreceding stage. Therefore, after the angular positions of the outputgear and the gear in the preceding stage have been respectivelydetermined with the first positioning part and the second positioningpart as a reference, when another gear is assembled between the outputgear and the gear in the preceding stage, the gear is assembled in astate that the phase of the output gear with the gear in the precedingstage is adjusted. Accordingly, the phase can be matched between thegears which are not engaged with each other directly. Further, differentfrom a case that the phase is matched by utilizing the tooth missingpart, a meshing ratio is not lowered even when the teeth number issmall.

In accordance with at least an embodiment of the present invention, thefirst positioning part is a first hole whose inner peripheral contourshape is a complete round shape, and the second positioning part is asecond hole whose inner peripheral contour shape is an elliptic or ovalshape in which its major axis is directed in a circumferential directionof the gear in the preceding stage. According to this structure, theangular position of the output gear is adjusted with a high degree ofaccuracy and a clearance of meshing is adjusted by the gear in thepreceding stage.

In accordance with at least an embodiment of the present invention, thefirst hole is formed with an inner peripheral wall part over an angularrange of 180° or more. According to this structure, the first pin isprevented from being inclined after the first pin is fitted to the firsthole until the assembling is completed.

In accordance with at least an embodiment of the present invention, theoutput gear is provided with a teeth formation part in which a pluralityof tooth parts are formed in a circumferential direction and a teethnon-formation part in which a tooth part is not formed, and the firstpositioning part is formed in the teeth non-formation part. According tothis structure, the first positioning part is easily formed and theteeth non-formation part functions as a stopper part. Therefore, afterthe gear mechanism has been assembled, even when the first pin isdetached, the output gear is prevented from being turned excessively.

In accordance with at least an embodiment of the present invention, thegear in the preceding stage is formed with a teeth formation part inwhich tooth parts are formed and a teeth non-formation part in which atooth part is not formed, and a stopper mechanism for determining anangular range of the output gear which is driven and turned by the motoris formed at an end part of the teeth non-formation part. In thisstructure, the phase of the output gear with the gear in the precedingstage is required to be matched. However, according to the embodiment ofthe present invention, even when the output gear and the gear in thepreceding stage are not engaged with each other directly, the phase canbe matched. In this case, the second positioning part may be formed onan inner peripheral side of the teeth non-formation part of the gear inthe preceding stage.

In accordance with at least an embodiment of the present invention,grease is applied to the teeth formation part of the output gear, and anangular range of the teeth formation part of the output gear is largerthan the angular range of the output gear which is driven and turned bythe motor. According to this structure, when grease is applied while theoutput gear is turned at the time of assembling of the geared motor, thegrease can be surely applied to the entire angular range of the outputgear which is driven and turned by the motor.

In accordance with at least an embodiment of the present invention, thegear in the preceding stage is an input gear of the gear mechanism intowhich rotation of the motor is firstly inputted. In this case, theoutput gear and the gear in the preceding stage are often not engagedwith each other directly. Even in this case, the phase of the outputgear with the gear in the preceding stage can be matched.

In accordance with at least an embodiment of the present invention, thegeared motor includes a case which accommodates the motor and the gearmechanism. The output gear is provided with a teeth formation part inwhich a plurality of tooth parts are formed in a circumferentialdirection and a teeth non-formation part in which a tooth part is notformed. The teeth non-formation part is provided with a small diameterpart which is located on an inner side in a radial direction withrespect to a tooth tip circle of the tooth part, and the output gear isdisposed to be located at a nearer position to an inner face of the casethan other gears of the gear mechanism and, when the output gear isdriven and turned by the motor, the small diameter part always faces theinner face of the case. According to this structure, although the outputgear is disposed to be located at a nearer position to the inner face ofthe case than other gears of the gear mechanism, the output gear isprovided with the teeth non-formation part having a small diameter partwhich is located on an inner side in a radial direction with respect toa tooth tip circle of the tooth part and, when the output gear is drivenand turned by the motor, the small diameter part always faces the innerface of the case. Therefore, the output gear can be disposed at a nearerposition to the inner face of the case and thus the size of the case canbe reduced.

In accordance with at least an embodiment of the present invention, thegeared motor includes a stopper mechanism which is provided at a midwayposition of the gear mechanism for determining an angular range of theoutput gear which is driven and turned by the motor. According to thisstructure, when the output gear is driven and turned by the gear in thepreceding stage, a tooth part of the gear in the preceding stage issurely prevented from engaging with the teeth non-formation part.

Other features and advantages of the invention will be apparent from thefollowing detailed description, taken in conjunction with theaccompanying drawings that illustrate, by way of example, variousfeatures of embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, withreference to the accompanying drawings which are meant to be exemplary,not limiting, and wherein like elements are numbered alike in severalFigures, in which:

FIGS. 1( a), 1(b) and 1(c) are explanatory views showing an entirestructure of a geared motor in accordance with an embodiment of thepresent invention.

FIG. 2 is a plan view showing a geared motor in accordance with anembodiment of the present invention in which a cover is detached.

FIGS. 3( a) and 3(b) are explanatory cross-sectional views showing aninternal structure of a geared motor in accordance with an embodiment ofthe present invention.

FIGS. 4( a) and 4(b) are explanatory perspective views showing a gearmechanism of a geared motor in accordance with an embodiment of thepresent invention.

FIGS. 5( a) and 5(b) are explanatory views showing an engaging portionof a motor pinion with a gear in a geared motor in accordance with anembodiment of the present invention.

FIGS. 6( a) and 6(b) are explanatory views showing a stopper mechanismwhich is structured between a motor pinion and a gear in a geared motorin accordance with an embodiment of the present invention.

FIG. 7 is a plan view showing an engaging portion of an output memberwith a gear in a geared motor in accordance with an embodiment of thepresent invention.

FIGS. 8( a), 8(b) and 8(c) are explanatory perspective views showing astate in which phase matching of a gear with a gear is performed when ageared motor is to be manufactured in accordance with an embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of a gear mechanism and a motor to which the presentinvention is applied will be described below with reference to theaccompanying drawings.

(Entire Structure)

FIGS. 1( a), 1(b) and 1(c) are explanatory views showing an entirestructure of a geared motor in accordance with an embodiment of thepresent invention. FIG. 1( a) is a perspective view showing a gearedmotor, FIG. 1( b) is an exploded perspective view showing a state inwhich a cover is detached from the geared motor, and FIG. 1( c) is anexploded perspective view showing a state in which a case is furtherdetached. FIG. 2 is a plan view showing a geared motor in accordancewith an embodiment of the present invention in which a cover isdetached. FIGS. 3( a) and 3(b) are explanatory cross-sectional viewsshowing an internal structure of a geared motor in accordance with anembodiment of the present invention. FIG. 3( a) is a cross-sectionalview showing a geared motor which is cut at a position corresponding tothe “S-S” line in FIG. 2, and FIG. 3( b) is a cross-sectional viewshowing a gear mechanism which is cut along the line “O-A-B-C-D-E” inFIG. 2.

In FIGS. 1( a), 1(b) and 1(c) and FIG. 2, a geared motor 1 to which thepresent invention is applied is substantially structured of a motor 2having a stepping motor structure, a gear mechanism 6 comprised of aplurality of gears, and a housing 5 in which the motor 2 and the gearmechanism 6 are accommodated. The housing 5 includes a cup-shaped case51 whose upper face is opened and a plate-shaped cover 52 which closesopening of the case 51.

As shown in FIG. 3( a), the motor 2 is substantially structured of astator 4 and a rotor 3. The stator 4 includes two stator assemblies 4 aand 4 b which are disposed so as to be superposed on each other in amotor axial direction “L”. In each of the stator assemblies 4 a and 4 b,an outer stator core 41 and an inner stator core 42 are disposed so asto be faced each other in the motor axial direction “L”. Each of theouter stator core 41 and the inner stator core 42 is provided with aflange part formed in a circular ring shape and pole teeth which arebent from an inner circumferential edge of the flange part in the motoraxial direction “L”. In a state that the outer stator core 41 and theinner stator core 42 are disposed in the motor axial direction “L”, thepole teeth of the outer stator core 41 and the pole teeth of the innerstator core 42 are alternately arranged in the circumferentialdirection.

The rotor 3 is coaxially disposed on an inner side of the stator 4. Therotor 3 includes a rotor main body 33 provided with a shaft hole 330 anda permanent magnet 31 which is fixed to an outer peripheral face of therotor main body 33. An outer peripheral face of the permanent magnet 31faces the pole teeth. The rotor 3 is rotatably supported by a supportshaft 70 which is fitted to the shaft hole 330. The support shaft 70 isa fixed shaft whose both ends are supported by a bottom part 510 of thecase 51 and the cover 52. An end part on a cover 52 side of the rotormain body 33 is formed as a rotation shaft 35 whose outer peripheralface is provided with a motor pinion 34. In the motor 2 structured asdescribed above, an outer stator core 41 of the stator assembly 4 bwhich is disposed on an opposite side to an output side “L1” where therotation shaft 35 is protruded (opposite-to-output side “L2”) is formedas a part of the case 51.

In each of two stator assemblies 4 a and 4 b, the outer stator core 41and the inner stator core 42 are superposed on each of a pair of flangeparts 88 formed in the coil bobbin 86. The flange part 88 is connectedwith a cylindrical tube part 87 surrounding around the pole teeth and acoil 45 is wound around in a region formed by the cylindrical tube part87 and the flange parts 88. The coil bobbin 86 is provided with aterminal holding part 85 having a larger wall thickness at a portionlocated on an outer side in a radial direction with respect to an endface on an output side “L1” of the stator 4. The terminal holding part85 is protruded to an outer side in the radial direction through acut-out portion 515 (see FIG. 1( c)) formed in a side face part of thecase 51. The terminal holding part 85 holds a plurality of motor sideterminals 99. An outer side in the radial direction of the terminalholding part 85 is covered with a terminal cover 11 and an outside cover12.

(Schematic Structure of Gear Mechanism 6)

FIGS. 4( a) and 4(b) are explanatory perspective views showing the gearmechanism 6 of the geared motor 1 in accordance with an embodiment ofthe present invention. FIG. 4( a) is a perspective view sowing the gearmechanism 6 and FIG. 4( b) is its exploded perspective view.

As shown in FIGS. 2 and 3( b) and FIGS. 4( a) and 4(b), the geared motor1 in this embodiment includes the gear mechanism 6 comprised of aplurality of gears including the motor pinion 34. Rotation of the rotor3 of the motor 2 is outputted to an outer side through the gearmechanism 6. In this embodiment, the gear mechanism 6 includes totaledfour gears 61, 62, 63 and 64 in addition to the motor pinion 34, and thegear 64 of a last stage is structured as an output member 640 providedwith an output shaft 641. The output shaft 641 of the output member 640is a plate-like part having a shape in which a round bar portion is cutout so as to form two opposed faces to each other. Therefore, a shape ofthe output shaft 641 is changed in a circumferential direction and amounting direction when a driven member (not shown) is to be connectedwith the output shaft 641 has directionality in the circumferentialdirection.

Three gears 61, 62 and 63 except the gear 64 of the last stage arerespectively rotatably supported by support shafts 71, 72 and 73 (seeFIG. 3( b)) whose both ends are supported by an intermediate plate 55which is fixed to the case 51 and the cover 52. The gear 64 of the laststage is rotatably supported so that its shaft parts 642 and 643 arerotatably supported by a bearing part 521 of the cover 52 and a bearingpart 551 of the intermediate plate 55. In this embodiment, theintermediate plate 55 is provided with a flat plate part 550 and a pairof connecting plates 556 and 557 which are stood up toward an outputside “L1” from positions opposite to each other of the flat plate part550. The connecting plates 556 and 557 are fixed to an inner face of thecase 51. Further, a center of the flat plate part 550 of theintermediate plate 55 is formed with a center hole 558 through which thesupport shaft 70, the rotation shaft 35 of the rotor 3 and the like arepenetrated. In this embodiment, the gears 61, 62 and 63 are a gear madeof resin such as polyacetal, polybutylene terephthalate or polyamide.

In this embodiment, when viewed from the motor pinion 34 side, a largediameter gear part 611 of a first gear 61 is engaged with the motorpinion 34 which is formed on an outer peripheral side of the output side“L1” of the rotation shaft 35. A small diameter gear part 612 of thegear 61 is engaged with a large diameter gear part 621 of a second gear62. A small diameter gear part 622 of the gear 62 is engaged with alarge diameter gear part 631 of a third gear 63 and a small diametergear part 632 of the gear 63 is engaged with teeth part 645 of the gear64 of the last stage. The gear mechanism 6 is structured as a speedreducing gear train as described above. In this embodiment, four gears61, 62, 63 and 64 are disposed around the motor pinion 34.

In the geared motor 1 structured as described above, when an electricalpower is supplied to the stator 4 of the motor 2 and thereby the rotor 3is rotated, the rotation is transmitted to the output member 640 (gear64) through the motor pinion 34, the gear 61, the gear 62 and the gear63 to turn the output shaft 641. In this embodiment, the rotor 3 iscapable of rotating in a clockwise direction “CW” and in acounterclockwise direction “CCW” and the output member 640 (gear 64) isreciprocatedly turned over a predetermined angular range according tothe rotation of the rotor 3. In this embodiment, the output shaft 641 ofthe output member 640 is a plate-like part having a shape in which around bar portion is cut out so as to form two opposed faces to eachother. Therefore, when a driven member (not shown) is connected with theoutput shaft 641 in a predetermined direction by utilizing thedirectionality of the output shaft 641, an attitude of the driven membercan be changed by utilizing rotation of the motor 2. In this case, aturning range in the clockwise direction “CW” and a turning range in thecounterclockwise direction “CCW” of the output member 640 are restrictedby a stopper mechanism which is structured between the motor pinion 34and the gear 61 as described below with reference to FIGS. 5( a) and5(b) and FIGS. 6( a) and 6(b). Therefore, a range in which an attitudeor the like of the driven member is changed is restricted by the stoppermechanism.

(Structure of Stopper Mechanism Between Motor Pinion 34 and Gear 61)

FIGS. 5( a) and 5(b) are explanatory views showing an engaging portionof the motor pinion 34 with the gear 61 in the geared motor 1 inaccordance with an embodiment of the present invention. FIG. 5( a) is aplan view showing an engaging portion of the motor pinion 34 with thegear 61 and FIG. 5( b) is an enlarged plan view showing the engagingportion. FIGS. 6( a) and 6(b) are explanatory views showing a stoppermechanism which is structured between the motor pinion 34 and the gear61 in the geared motor 1 in accordance with an embodiment of the presentinvention. FIG. 6( a) is a plan view showing a state just beforerotation of the motor pinion 34 is stopped by a stopper mechanism andFIG. 6( b) is a plan view showing a state that rotation of the motorpinion 34 has just been stopped by the stopper mechanism.

In FIGS. 5( a) and 5(b), the motor pinion 34 (first gear) is formed withtooth parts 345 over the entire periphery and the number of teeth isnine in this embodiment. The motor pinion 34 is engaged with the largediameter gear part 611 of the gear 61. The large diameter gear part 611of the gear 61 is formed with a stopper part 8 which is capable ofengaging with a tooth part 345 of the motor pinion 34 to stop andprevent rotation of the motor pinion 34. More specifically, an outerperipheral part of the large diameter gear part 611 of the gear 61 isformed with a teeth formation part 616 where tooth parts 615 are formedand a teeth non-formation part 617 where tooth parts 615 are not formed.Both ends in a circumferential direction of the teeth non-formation part617 functions as the stopper part 8.

In this embodiment, at both ends in the circumferential direction of theteeth non-formation part 617, i.e., in each of two boundary portionsbetween the teeth formation part 616 and the teeth non-formation part617, the teeth non-formation part 617 is formed with a protruded part617 a, which is protruded to an outer side in a radial direction withrespect to the tooth tip circle “F61” of the tooth parts 615 of the gear61, and a recessed part 617 b which is recessed to an inner side in theradial direction with respect to the protruded part 617 a on a teethnon-formation part 617 side so as to be adjacent to the protruded part617 a on an opposite side to the teeth formation part 616 in thecircumferential direction. The protruded part 617 a and the recessedpart 617 b are connected with each other in the circumferentialdirection.

In this embodiment, the recessed part 617 b is recessed to an inner sidein the radial direction with respect to the tooth tip circle “F61” ofthe gear 61. However, the recessed part 617 b is located on an outerside in the radial direction with respect to the pitch circle “P61” ofthe gear 61. The pitch circle “P61” of the gear 61 is located betweenthe tooth root circle “R61” and the tooth tip circle “F61” and thus therecessed part 617 b is located on an outer side in the radial directionwith respect to the middle of the tooth root circle “R61” and the toothtip circle “F61”. In other words, the recessed part 617 b is located onan outer side in the radial direction with respect to an imaginarycircle having a diameter between a diameter of the tooth root circle“R61” and a diameter of the tooth tip circle “F61” and is concentricwith the tooth root circle “R61” and the tooth tip circle “F61”. In thisembodiment, the recessed part 617 b is structured as a peripheral face(circular arc face) having a peripheral length substantially equal to alength for one of the tooth parts 615. Further, a portion of the teethnon-formation part 617 which is interposed in the circumferentialdirection between two recessed parts 617 b is formed in a peripheralface (circular arc face) which is extended in the circumferentialdirection on a concentric imaginary circle having the same diameter asthe tooth tip circle “F61”.

In the gear mechanism 6 structured as described above, when the motorpinion 34 is rotated and the tooth part 345 of the motor pinion 34 isreached to an end part of the teeth formation part 616 as shown in FIG.6( a), the tooth part 345 of the motor pinion 34 is abutted with theprotruded part 617 a of the gear 61 and, immediately after that time, asshown in FIG. 6( b), the tooth part 345 of the motor pinion 34 isabutted with the recessed part 617 b. As a result, rotation of the motorpinion 34 is stopped. At the time of the stopping operation, as shown inFIG. 6( a), when the tooth part 345 of the motor pinion 34 is abuttedwith the protruded part 617 a of the gear 61, a portion of the toothpart 345 corresponding to the pitch circle “P34” is abutted with theprotruded part 617 a of the gear 61. In this case, a side face of theprotruded part 617 a of the gear 61 is inclined and thus a pressureangle is large when the portion of the tooth part 345 corresponding tothe pitch circle “P34” is abutted with the protruded part 617 a. Forexample, the pressure angle is not less than 50°. Therefore, the motorpinion 34 is braked. Further, as shown in FIG. 6( b), when a tip endside of the tooth part 345 of the motor pinion 34 is to be abutted withthe recessed part 617 b, a portion which is near to the root part sidefrom the tip end side of the tooth part 345 is abutted with the recessedpart 617 b of the gear 61. Therefore, a load when the motor pinion 34 isstopped is shared between an abutting portion of a portion of the toothpart 345 corresponding to the pitch circle “P34” with the protruded part617 a and an abutting portion of the tip end side of the tooth part 345with the recessed part 617 b of the gear 61.

As described above, in the gear mechanism 6 and the geared motor 1 inthis embodiment, in order to structure the stopper mechanism whichutilizes engagement of the motor pinion 34 (first gear) and the gear 61(second gear), the gear 61 is formed with the stopper part 8 formed ofthe teeth non-formation part 617 where the tooth parts 615 are notformed and the teeth non-formation part 617 (stopper part 8) is formedwith the protruded part 617 a which is protruded to an outer side in theradial direction with respect to the tooth tip circle “F61” of the gear61 and the recessed part 617 b which is recessed to an inner side in theradial direction with respect to the protruded part 617 a at a positionadjacent to the protruded part 617 a in the circumferential direction.Therefore, when the tooth part 345 of the motor pinion 34 is abuttedwith the recessed part 617 b of the teeth non-formation part 617, theprotruded part 617 a is also abutted with the vicinity of the pitchcircle “P34” of the tooth part 345 of the motor pinion 34. Accordingly,even when rotation of the motor pinion 34 is stopped by the teethnon-formation part 617 (stopper part 8) provided in the gear 61, aturning force of the motor pinion 34 does not concentrate on the toothtip part of the tooth part 345 and thus damage such as breaking,deformation, a crack and the like is hard to be occurred in the toothpart 345.

Further, the recessed part 617 b is recessed to an inner side in theradial direction with respect to the tooth tip circle “F61” of the gear61. Therefore, the protruded part 617 a is surely abutted with thevicinity of the pitch circle “P34” of the tooth part 345 of the motorpinion 34 before the tooth part 345 of the motor pinion 34 is abuttedwith the recessed part 617 b. Accordingly, when rotation of the motorpinion 34 is stopped by the teeth non-formation part 617 provided in thegear 61, a turning force of the motor pinion 34 is surely prevented fromconcentrating on the tooth tip part of the tooth part 345 and thusdamage of the tooth part 345 is further hard to be occurred.

In addition, the recessed part 617 b is located on an outer side in theradial direction with respect to the pitch circle “P61” of the gear 61.In other words, the recessed part 617 b is located on an outer side inthe radial direction with respect to an imaginary circle having a middlediameter between the diameter of the tooth root circle “R61” and thediameter of the tooth tip circle “F61” of the gear 61 and is concentricwith the tooth root circle “R61” and the tooth tip circle “F61”.Therefore, a state is prevented in which tooth parts 345 adjacent toeach other in the circumferential direction of the motor pinion 34engage and bite the protruded part 617 a from both sides to be in anunmoving state.

Further, in this embodiment, the first gear which structures the stoppermechanism is the motor pinion 34 provided in the rotation shaft 35 ofthe motor 2 and the second gear is the gear 61 (input gear) engaged withthe motor pinion 34. Therefore, the stopper mechanism (stopper part 8)is provided in a portion where a torque is relatively small and thus aload applied to the tooth part 345 is small. Accordingly, damage of thetooth part 345 is hard to be occurred.

(Structure of Output Member 640)

FIG. 7 is a plan view showing an engaging portion of the output member640 with the gear 63 in the geared motor 1 in accordance with anembodiment of the present invention.

As shown in FIG. 7, in the gear mechanism 6 of the geared motor 1 inthis embodiment, a small diameter gear part 632 of the gear 63 is formedwith tooth parts 635 over the entire periphery. The number of the teethis ten in this embodiment. On the other hand, an outer peripheral partof the output gear 64 (output member 640) engaged with the smalldiameter gear part 632 of the gear 63 is formed with a teeth formationpart 646 where a plurality of tooth parts 645 is formed in acircumferential direction and a teeth non-formation part 647 where thetooth part 645 is not formed. Therefore, the teeth non-formation part647 of the output gear 64 functions as a stopper part which is engagedwith the tooth part 635 of the gear 63 to prevent turning of the gear63.

In this embodiment, the teeth non-formation part 647 is provided with asmall diameter part 647 a formed in a circumferential face (circular arcface), which is located on an inner side in the radial direction withrespect to the tooth tip circle “F64” of the tooth part 645, and largediameter parts 647 b and 647 c having a larger diameter than the smalldiameter part 647 a at positions interposed by the small diameter part647 a and the teeth formation part 646. The large diameter parts 647 band 647 c are formed in a circumferential face (circular arc face)having the same diameter as the tooth tip circle “F64”.

In the geared motor 1 which is structured as described above, the outputgear 64 (output member 640) is located at a nearer position to an innerface 519 of the case 51 than other gears 61, 62 and 63. However, whenthe output member 640 is turned according to rotation of the motor 2,the small diameter part 647 a is set to always face the inner face 519of the case 51. Therefore, the output member 640 can be disposed in thevicinity of the inner face 519 of the case 51. Accordingly, the size ofthe case 51 can be reduced, in other words, the diameters of the housing5 and the geared motor 1 can be reduced.

In the gear mechanism 6 of the geared motor 1 structured as describedabove, an angular range over which the output member 640 is turned bythe motor 2 is an angle (θa) determined by the stopper part 8 of thegear 61 which is described with reference to FIGS. 5( a) and 5(b) andFIGS. 6( a) and 6(b). On the other hand, an angular range of the teethformation part 646 of the output member 640 is “θb”, which is largerthan the angular range “θa” over which the output member 640 is turnedby the motor 2. Therefore, when the output member 640 is turned by thegear 63, the tooth part 635 of the gear 63 does not engage with theteeth non-formation part 647.

Grease is applied to the gears used in the gear mechanism 6. Therefore,grease 9 is also applied to the tooth parts 645 of the output member640. In this embodiment, the angular range over which the output member640 is turned by the motor 2 is “θa”. However, the grease 9 is appliedover the entire angular range “θb” which is wider than the angular range“θa”. In other words, in this embodiment, since the angular range “θb”of the teeth formation part 646 is wider than the angular range “θa”over which the output member 640 is turned by the motor 2, at the timeof assembling of the geared motor 1, the grease 9 is applied while theoutput member 640 is turned. In this case, the output member 640 can beturned over the angular range “θb” of the teeth formation part 646 andthus the grease 9 is surely applied over the entire angular range “θa”over which the output member 640 is turned by the motor 2.

(Phase Matching of Gear 61 with Output Gear 64 (Output Member 640))

FIGS. 8( a), 8(b) and 8(c) are explanatory perspective views showing astate in which phase matching of the gear 61 with the output gear 64 isperformed when the geared motor 1 is to be manufactured in accordancewith an embodiment of the present invention.

As described with reference to FIGS. 5( a) and 5(b) and FIGS. 6( a) and6(b), the stopper part 8 is structured in the gear 61 and the angularrange over which the output gear 64 (output member 640) is turned is setby “θa” by the stopper part 8. Further, a driven member is connectedwith the output shaft 641 of the output member 640 in a predetermineddirection. Therefore, a phase between the gear 61 and the output gear 64(output member 640) is required to be matched. However, the gear 61 isan input gear to which rotation of the motor 2 is firstly inputted andis a preceding gear (gear in the preceding stage) connected with theoutput gear 64 (output member 640) through the gears 62 and 63. In otherwords, the gear 61 and the output gear 64 are not engaged with eachother directly.

Therefore, in this embodiment, as shown in FIG. 7 and the like, theoutput gear 64 is formed with a first hole 649 (first positioning part)showing an angular position of the output gear 64. In this embodiment,the first hole 649 is formed by utilizing the teeth non-formation part647 of the output gear 64. More specifically, the first hole 649 isformed in the large diameter part 647 c of the teeth non-formation part647 whose peripheral length is longer than the large diameter part 647b. In this embodiment, the first hole 649 as the first positioning partis formed so that a part of the hole is located and opened at an outeredge of the large diameter part 647 c but its inner peripheral contourshape is formed in a complete round shape. Therefore, although the firsthole 649 is not a complete circular hole, the inner peripheral wall part649 a is formed over an angular range of 180° or more and thus the firsthole 649 sufficiently functions as a positioning recessed part. In thisembodiment, the inner peripheral wall part 649 a of the first hole 649is formed in an angular range of approximately 200°.

On the other hand, as shown in FIGS. 5( a) and 5(b) and the like, thegear 61 is formed with a second hole 619 (second positioning part)showing an angular position of the gear 61 on an inner peripheral sideof the teeth non-formation part 617 of the gear 61. In this embodiment,the second hole 619 is formed in a portion corresponding to the teethnon-formation part 617 of the large diameter gear part 611 of the gear61. An inner peripheral contour shape of the second hole 619 as thesecond positioning part is formed in an elliptic shape or an oval shapewhose major axis is directed in a circumferential direction so that anangular position of the gear 61 is capable of being finely adjusted.

Therefore, when the gear mechanism 6 is to be assembled in themanufacturing step for the geared motor 1, first, as shown in FIG. 8(a), a first pin 91 formed in a round bar shape and a second pin 92formed in a round bar shape are stood up on an inner side of the centerhole 558 of the intermediate plate 55 in a state that the support shafts71, 72 and 73 are attached to the intermediate plate 55 by utilizing ajig (not shown). The first pin 91 is stood up at a predetermined angularposition with the turning center of the gear 64 (bearing part 551) asthe center and the second pin 92 is stood up at a predetermined angularposition with a turning center of the gear 61 (support shaft 71) as thecenter.

Next, the output member 640 and the gears 61, 62 and 63 are attached.When the output member 640 is to be attached to the bearing part 551, asshown in FIG. 8( b), a position where the first hole 649 as the firstpositioning part is fitted to the first pin 91 is set to be anassembling angular position of the output member 640. Further, when thegear 61 is to be fitted to the support shaft 71, a position where thesecond hole 619 as the second positioning part is fitted to the secondpin 92 is set to be an assembling angular position of the gear 61.

After that, as shown in FIG. 8( c), the gear 63 is meshed with theoutput member 640. Further, the gear 62 is meshed with the gear 63. Inthis case, when the gear 62 is to be meshed with the gear 61, the secondhole 619 is formed in an elliptic shape or an oval shape and thus, in astate that the second pin 92 is fitted into the second hole 619, thegear 62 and the gear 61 are meshed while an angular position of the gear61 is finely adjusted.

When the gear mechanism 6 is assembled on the intermediate plate 55 asdescribed above, the phase of the gear 61 with the output gear 64(output member 640) is matched.

As described above, in this embodiment, the output member 640 is formedwith the first hole 649 as the first positioning part showing theangular position of the output member 640 and the gear 61 in thepreceding stage which is connected with the output member 640 throughthe gears 62 and 63 is formed with the second hole 619 as the secondpositioning part showing the angular position of the gear 61. Therefore,after the angular positions of the output member 640 and the gear 61 inthe preceding stage have been respectively determined with the firsthole 649 and the second hole 619 as a reference, when the gears 62 and63 are assembled between the output member 640 and the gear 61 in thepreceding stage, the gears 62 and 63 are assembled in a state that thephase of the output member 640 with the gear 61 in the preceding stageis adjusted. Accordingly, the phase can be adjusted between the gearswhich are not engaged with each other directly. Further, different froma case that the phase is matched by utilizing the tooth missing part, ameshing ratio is not lowered even when the teeth number is small.

In this embodiment, although the first hole 649 is not formed in acomplete circular hole but the inner peripheral contour shape of thefirst hole 649 is a complete round shape and the inner peripheralcontour shape of the second hole 619 is an elliptic shape or an ovalshape whose major axis is directed in the circumferential direction ofthe gear 61. Therefore, the angular position of the output member 640can be adjusted with a high degree of accuracy and a clearance ofmeshing can be adjusted by the gear 61 in the preceding stage.

Further, the inner peripheral wall part 649 a of the first hole 649 isformed over an angular range of 180° or more and thus, the first pin 91is prevented from being inclined after the first pin 91 is fitted to thefirst hole 649 until the assembling is completed. Therefore, in thisembodiment, when the inner peripheral wall part 649 a is formed over anangular range of 180° or more, the recessed part having the innerperipheral wall part 649 a may correspond to the first hole 649 as thefirst positioning part.

Further, as described with reference to FIG. 7 and the like, the outputmember 640 is formed with the teeth formation part 646 where a pluralityof tooth parts 645 is formed in the circumferential direction and theteeth non-formation part 647 where the tooth part 645 is not formed, andthe teeth non-formation part 647 functions as a stopper part. Therefore,after the gear mechanism 6 has been assembled, even when the first pin91 is detached, the output member 640 is prevented from being turnedexcessively. Further, in this embodiment, the first hole 649 as apositioning part of the output gear 64 is formed in the teethnon-formation part 647 and thus, in comparison with a case that thefirst hole 649 is formed in the teeth formation part 646, the first hole649 (positioning part) is formed easily.

Other Embodiments

In the embodiment described above, the stopper part 8 is formed in theinput gear (gear 61). However, the stopper part 8 may be formed in othergears 62 and 63 or the like.

In the embodiment described above, the stopper part 8 is provided in thegear mechanism 6 of the geared motor 1 in which the motor 2 is used as adrive source. However, the present invention may be applied to a case inwhich the stopper part 8 is provided in the gear mechanism 6 of a deviceother than the geared motor 1 in which the motor 2 is used as a drivesource.

In the embodiment described above, the stopper part 8 is formed with theprotruded parts 617 a provided at two positions separated from eachother in the circumferential direction and the recessed part 617 b isformed for each of two protruded parts 617 a. However, the recessedparts 617 b may be formed as one continuous recessed part 617 b betweentwo protruded parts 617 a.

In the embodiment described above, the first hole 649 and the secondhole 619 are utilized to adjust angular positions of the gear 61 (gearin the preceding stage) and the gear 64 (output gear). However, thefirst hole 649 and the second hole may be utilized to adjust angularpositions of the gear 64 (output gear) and other gears 62 and 63.Further, the first hole 649 may be formed in a complete round shape inwhich its outer peripheral portion is not cut out. Alternatively, acut-out part which is formed by cutting out an outer peripheral face ofthe output gear 64 may be used as the first positioning part. The secondhole 619 may be formed in a circular shape other than an elliptic shapeand an oval shape. Further, a cut-out part which is formed by cuttingout an outer peripheral face of the teeth non-formation part 617 of thegear 61 may be used as the second positioning part.

In the embodiment described above, three gears 61, 62 and 63 aredisposed between the motor pinion 34 and the gear 64. However, thepresent invention may be applied to the gear mechanism 6 in which onegear or four or more gears are disposed between the motor pinion 34 andthe gear 64.

While the description above refers to particular embodiments of thepresent invention, it will be understood that many modifications may bemade without departing from the spirit thereof. The accompanying claimsare intended to cover such modifications as would fall within the truescope and spirit of the present invention.

The presently disclosed embodiments are therefore to be considered inall respects as illustrative and not restrictive, the scope of theinvention being indicated by the appended claims, rather than theforegoing description, and all changes which come within the meaning andrange of equivalency of the claims are therefore intended to be embracedtherein.

What is claimed is:
 1. A geared motor comprising: a motor; and a gearmechanism which transmits rotation of the motor; wherein the gearmechanism comprises an output gear which outputs rotation of the motorand a gear in a preceding stage which is connected with the output gearthrough another gear; wherein the output gear is provided with a teethformation part in which a plurality of tooth parts are formed in acircumferential direction and a teeth non-formation part in which atooth part is not formed, the output gear being formed with a firstpositioning part showing an angular position of the output gear, thefirst positioning part being formed in the teeth non-formation part;wherein the gear in the preceding stage is formed with a secondpositioning part showing an angular position of the gear in thepreceding stage, the gear in the preceding stage being formed with ateeth formation part in which tooth parts are formed and a teethnon-formation part in which a tooth part is not formed; and wherein astopper mechanism for determining an angular range of the output gearwhich is driven and turned by the motor is formed at an end part of theteeth non-formation part of the gear in the preceding stage.
 2. Thegeared motor according to claim 1, wherein the first positioning part isa first hole whose inner peripheral contour shape is a complete roundshape, and the second positioning part is a second hole whose innerperipheral contour shape is an elliptic or oval shape in which its majoraxis is directed in a circumferential direction of the gear in thepreceding stage.
 3. The geared motor according to claim 2, wherein thefirst hole is formed with an inner peripheral wall part over an angularrange of 180° or more.
 4. The geared motor according to claim 1, whereinthe second positioning part is formed on an inner peripheral side of theteeth non-formation part of the gear in the preceding stage.
 5. Thegeared motor according to claim 1, wherein grease is applied to theteeth formation part of the output gear, and an angular range of theteeth formation part of the output gear is larger than the angular rangeof the output gear which is driven and turned by the motor.
 6. Thegeared motor according to claim 1, wherein the gear in the precedingstage is an input gear of the gear mechanism into which rotation of themotor is firstly inputted.
 7. The geared motor according to claim 1,further comprising a case which accommodates the motor and the gearmechanism, wherein the teeth non-formation part of the output gear isprovided with a small diameter part which is located on an inner side ina radial direction with respect to a tooth tip circle of the tooth partof the output gear, and wherein the output gear is disposed to belocated at a nearer position to an inner face of the case than othergears of the gear mechanism and, when the output gear is driven andturned by the motor, the small diameter part always faces the inner faceof the case.
 8. The geared motor according to claim 7, wherein grease isapplied to the teeth formation part of the output gear, and an angularrange of the teeth formation part of the output gear is larger than theangular range of the output gear which is driven and turned by themotor.
 9. The geared motor according to claim 1, wherein the gear in thepreceding stage is a gear having a large diameter gear part which isdirectly engaged with a motor pinion of the motor, and an outerperipheral part of the large diameter gear part of the gear is formedwith the teeth formation part and the teeth non-formation part.